A billionaire Hamburg fan has loaned the Bundesliga club 17 million euros to help them finance their summer squad building.

International transport tycoon Klaus-Michael Kuhne, 77, dipped into his estimated five billion euro fortune to help out his favourite team, who can now pay the 4.5 million euros Mainz are seeking for Nicolai Muller.

The 26-year-old Germany international is due to undergo a medical at HSV on Tuesday, and German media speculate the six-time champions, who have just signed Valon Behrami from Napoli, could now also make a move for Augsburg left-back Matthias Ostrzolek.

"We're delighted with this big commitment from Mr Kuhne, and his faith in us. Given our new setup, this show of support comes just at the right time," Hamburg chairman Dietmar Beiersdorfer said.

"With future cooperation, we know that we have a long-term investor on our side."